1. Field of the Invention
The present disclosure relates to azeotrope and azeotrope-like compositions of fluorocarbon compounds. In particular, the present disclosure relates to an azeotrope composition comprising octafluorocyclobutane and 1,1,1,2,2,3-hexafluoropropane and an azeotrope composition comprising octafluorocyclobutane and hydrogen fluoride that are useful in processes to manufacture and purify fluorocarbons.
2. Description of Related Art
Halogenated compounds, especially fluorinated compounds, such as fluorocarbons and hydrofluorocarbons, have been widely used in the industry as for instance, refrigerants, solvents, cleaning agents, foam expansion agents, aerosol propellants, heat transfer media (e.g., heat transfer fluids, and refrigerants), dielectrics, fire extinguishing agents, sterilants and power cycle working fluids.
Processes for the production of 1,1,1,2,2,3-hexafluoropropane (HFC-236cb) by reaction of tetrafluoroethylene monomer (CF2═CF2 or TFE) with difluoromethane (CH2F2 or HFC-32) in the presence of antimony pentafluoride (SbF5) catalyst have been described in U.S. Pat. No. 6,184,426.
Current commercially produced TFE is a monomer in the manufacture of a variety of fluorinated polymers, such as polytetrafluoroethylene (PTFE), among others. The various processes used for the manufacture of TFE monomer frequently produce a variety of co-products that are unacceptable in a polymer feedstock, and these TFE monomer manufacturing processes incur significant expense both in equipment and operating costs to remove any such co-products down to low levels to produce high-purity TFE. These purification steps typically increase the production costs for TFE by as much as 20%. Such co-products are considered unacceptable in the TFE starting material because of their adverse effect on the properties of the polymer materials produced from the TFE.
Octafluorocyclobutane (cyclo-C4F8, or PFC-C318) is one such co-product that may be produced in the manufacture of TFE. TFE used in a reaction with HFC-32 to produce HFC-236cb need not be purified to the same degree as that used as monomer, and may therefore contain some amount of PFC-C318. HFC-236cb may be used as a starting material for the production of certain fluoroolefins, which have been suggested as low global warming alternatives to existing working fluids such as those mentioned previously. If PFC-C318 is present in the TFE feedstock to produce HFC-236cb, it is expected to remain unreacted through the process and be removed with the HFC-236cb product.
It has been surprisingly discovered that PFC-C318 and HFC-236cb form an azeotrope composition. This azeotrope may be useful in various separation schemes to ultimately allow the production of HFC-236cb with appropriate purity to be used in processes for the manufacture of other fluorocarbons including fluoroolefins.